History
A 17-year-old woman is brought to the accident and emergency department by ambu-lance. She had collapsed in the high street; witnesses called an ambulance immediately as she began to fit. She had two further fits on the way to hospital and the paramedical team described classic generalized tonic–clonic seizures, including a stereotypical ictal cry. She is drowsy and confused on arrival. Her Medi-Alert bracelet confirms that she is known to have epilepsy and that she has another diagnosis, ‘XP’. Her family are on their way to the hospital. In the meantime the medical team ensures that she is now stable.
Examination
She appears to be in a deep sleep and is difficult to rouse, although she withdraws from pain. Her blood pressure is 105/60 mmHg, heart rate 68 beats/min and respiratory rate 12 breaths/min. She is clearly still in a post-ictal state. There are marked skin changes affecting all exposed areas of skin, particularly her face (especially cheeks, nose and pinna of her ears), neck, ‘V’ of the chest and the dorsa of her hands, but not affecting her trunk or other clothed areas. There is poikiloderma (skin atrophy, and telangiectasias with mottled hyperpigmentation and hypopigmentation) (Fig. 94.1). She has bilateral ectropions and a narrow ‘pinched’ nose.
Questions
• The distribution of the skin changes suggests a role for what environmental factor?
• What is XP?
• What skin complications can occur in XP?
Medicine
The distribution of this patient’s skin changes is typical for a photodermatosis, occurring on sites most exposed to direct sunlight. Areas more protected from sunlight – such as the scalp, upper eyelids, infranasal and submental areas, as well as fully clothed areas –are typically spared. The changes described are chronic and this is likely to represent a longstanding condition. The most common causes for photosensitive eruptions include drug reactions; however, although neuroleptic medications such as phenothiazines may be implicated, anti-epileptic medications are not particularly associated with phototoxic eruptions except in the context of porphyria. The only porphyria with prominent chronic cutaneous findings is porphyria cutanea tarda (PCT) (acute photosensitivity is seen in other cutaneous porphyrias). PCT is characterized by skin fragility with tense haemor- rhagic vesicles and bullae over sun-exposed sites, with hypertrichosis, atrophy and milia developing.
XP stands for xeroderma pigmentosum, a rare autosomal recessive disorder character-ized by a cellular hypersensitivity to ultraviolet (UV) radiation resulting from a defect in DNA repair. Individuals with XP develop multiple cutaneous neoplasms at a young age (from 4 to 5 years of age). All forms of skin cancer are described in XP, including basal cell carcinomas, squamous cell carcinomas and malignant melanoma. They are more prevalent over sun-exposed skin, but can also affect the eyes and even buccal mucosa.
Neurological problems, including epilepsy, ataxia, spasticity or developmental delay, are present in approximately 20 per cent of patients with XP.
The goals of treatment of patients with XP are to minimize morbidity and prevent mor-tality primarily through sun protection, through use of sunscreens and sun avoidance measures. Regular skin surveillance, as well as ophthamological and neurological review, are part of routine care of patients with XP.
KEY POINTS
• Xeroderma pigmentosa (XP) is a rare autosomal recessive skin disorder characterized by dramatic and early-onset photodamage of sun-exposed areas of the skin.
• XP is caused by an inherited defect in repair of UV-induced DNA damage.
• Skin cancers arise from a young age, are typically multiple and result in significant morbidity and potentially early death.
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